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ABSTRACT. The extraction of high-quality genomic DNA from Prosopis spp for polymerase chain reaction (PCR) amplification is complicated, owing to the presence of a high percentage of secondary metabolites that bind to or co-precipitate with nucleic acids. In the present study, we report a modified sodium dodecyl sulfate/phenol protocol that eliminates the use of liquid nitrogen in the maceration process, β-mercaptoethanol in the buffer extraction, and the ethanol precipitation step. The A 260 /A 280 absorbance ratios of the isolated DNA were approximately 2.0 to 1.9, suggesting that the DNA fraction was pure and can be used for further PCR analysis. The DNA isolated by this protocol is of sufficient quality for molecular applications; this technique could be applied to other organisms that have similar substances that hinder DNA extraction. Finally, this proposal represents an alternative fast, cheap, and effective method for the isolation of genomic DNA from fresh leaves of Prosopis spp, even in low-technology laboratories.

La extracción de ARN genómico de alta calidad para la amplificación por PCR, a partir de Prosopis spp., es complicada debido a la presencia de un alto porcentaje de metabolitos secundarios que se unen o coprecipitan con los ácidos nucleicos. En el presente estudio reportamos un protocolo modificado de sodio dodecil sulfato/fenol que incluye la eliminación de nitrógeno líquido en el proceso de maceración, β-mercaptoetanol en la extracción de tampón y paso de precipitación de etanol. Las proporciones de absorbancia A260/A280 del ARN aislado estaban en torno a 2 a 1.9, lo que sugiere que la fracción de ADN era pura y se puede usar para un análisis de PCR posterior. El ARN aislado por este protocolo es de calidad suficiente para aplicaciones moleculares; Esta técnica podría aplicarse a otros organismos que tienen sustancias similares que dificultan la extracción del ARN. Por último, esta propuesta representa una alternativa rápida, barata y eficaz para el aislamiento del ARN genómico de las hojas frescas de Prosopis spp., incluso en los laboratorios de baja tecnología.

The effect of copper toxicity on the photosynthetic activities and bioaccumulation in different tissues of Prosopis juliflora was investigated using three CuSO 4 concentrations (10, 50 and 100 mM) added under hydroponic conditions. Copper concentration and chlorophyll fluorescence were measured after 48 h of copper stress. The results obtained in this study show that increasing levels of 50 and 100 mM Cu 2+ resulted in a significant accumulation of this metal mainly in roots compared with control roots. On the other hand, our result showed a significant reduction of maximum photochemical efficiency of photosystem II (Fv/Fm) and the activity of photosystem II (F v /F 0 ) ratios in P. juliflora leaf treated with 100 mM Cu 2+ with respect to control after 4h of exposure. These changes suggested that the photosynthetic apparatus of P. juliflora was the primary target of the Cu 2+ action. Therefore the information provided by this short-term (48 h) experiment in P. juliflora showed that several physiological processes are activated, in which the copper uptake by roots and their accumulation in tissues play a central role. In conclusion, the chlorophyll fluorescence parameters can be used as a useful physiological tool to assess early changes in photosynthetic performance of P. juliflora in response to copper pollution in short-term. Finally, the present study showed that P. juliflora is a promising prospect for heavy metals phytoremediation purposes occurring in arid and semi-arid climates in the northwest Mexico.

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